<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>-</title>
    //-0,返回均为number类型
    <script type="text/javascript">
        console.log(typeof true,typeof (true-0),true-0);
        console.log(typeof '111',typeof ('111'-0),'111'-0);
        console.log(typeof null,typeof (null-0),null-0);
        console.log(typeof undefined,typeof (undefined-0),undefined-0);
        console.log(typeof 'asd',typeof ('asd'-0),'asd'-0);
    </script>
</head>
<body>

</body>
</html>